platform/x86: thinkpad_acpi: fix documentation for adaptive keyboard

The different values were offset by 1. 0 is for "home mode", 1 for
"web-browser mode", etc. Moreover, the URL to the laptop's user guide
did not work anymore.
Signed-off-by: Vincent Bernat <vincent@bernat.ch>
Link: https://lore.kernel.org/r/20211109195209.176905-1-vincent@bernat.chSigned-off-by: Hans de Goede <hdegoede@redhat.com>

Documentation/admin-guide/laptops/thinkpad-acpi.rst

@@ -1520,15 +1520,15 @@ This sysfs attribute controls the keyboard "face" that will be shown on the
 Lenovo X1 Carbon 2nd gen (2014)'s adaptive keyboard. The value can be read
 and set.
 
-- 1 = Home mode
-- 2 = Web-browser mode
-- 3 = Web-conference mode
-- 4 = Function mode
-- 5 = Layflat mode
+- 0 = Home mode
+- 1 = Web-browser mode
+- 2 = Web-conference mode
+- 3 = Function mode
+- 4 = Layflat mode
 
 For more details about which buttons will appear depending on the mode, please
 review the laptop's user guide:
-http://www.lenovo.com/shop/americas/content/user_guides/x1carbon_2_ug_en.pdf
+https://download.lenovo.com/ibmdl/pub/pc/pccbbs/mobiles_pdf/x1carbon_2_ug_en.pdf
 
 Battery charge control
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